CVE-2022-39374Network attack vector

Room denial of service via rejected-event admission

Published May 26, 2023 · Updated Feb 13, 2025

State-resolution failure in Matrix.org Synapse 1.62.0 through 1.67.0 allows remote attackers to disrupt federated room traffic. The state-resolution code rechecks authorization against room state and admits events previously rejected for citing rejected authorization events. Exploitation requires an attacker-controlled homeserver to share a room with the target; subsequent target messages and state changes are rejected in that room.

CVSS severity6.5
Medium
EPSS probability0.94%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

State-resolution failure in Matrix.org Synapse 1.62.0 through 1.67.0 allows remote attackers to disrupt federated room traffic. The state-resolution code rechecks authorization against room state and admits events previously rejected for citing rejected authorization events. Exploitation requires an attacker-controlled homeserver to share a room with the target; subsequent target messages and state changes are rejected in that room.

The record

CVE
CVE-2022-39374
Published
May 26, 2023
Updated
Feb 13, 2025
Vendor
Matrix.org
Product
Synapse
Classifications
CWE-400, T1499
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. May 26, 2023CVE publishedPublication date reported by the CVE source.
  2. Feb 13, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=>= 1.62.0, < 1.68.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Matrix.org · Synapseversion=>= 1.62.0, < 1.68.0

Published CVSS scores

6.5GitHub, Inc.CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
6.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-400Uncontrolled Resource Consumption
T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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